What we did (I learned from the Tahitians) was to tie a long rope onto the back of the panga and let it drift in front of you through the pass. The current would carry the boat along but the rope was still a way to stay in contact. We would dive and spear these little fish (compared to So Cal fish) and get them into the boat before the bad guys came along and mistook you for the fish. like you say we would have to start the dive out in the open blue water and just drift along near the bottom before surfacing always hold the speared fish as close to your chest as possible -otherwise the bad guys would rip em up and the Kia Ora restaurant wouldn't accept them. The Tahitian I dove with made his living off providing fish to Kia Ora and running a glass bottom shark sighting boat within the lagoon itself. He and I would feed the sharks while the "tourists" (including my wife) would take photos from inside. His wife was one of the dancers at Kia Ora. When we left for Huihine I gave him my long fins and a small speargun for taking me around. Good guy-wish I could remember his name. He did not care for the French dive master at all ! Neither did I. He was a jerk.